Modern mobile devices are configured for communication with various external transmitters, receivers and transceivers to enable a variety of wireless functions. For example, mobile phones are capable of hosting mobile phone calls, wirelessly accessing the Internet and playing programs broadcast by AM/FM radio stations. Antennas housed within these mobile devices are used to transmit and receive electromagnetic signals to/from the various transmitters, receivers and transceivers through the modulation of various properties (e.g., amplitude, frequency, pulse width, phase) of electromagnetic waves. These antennas are connected to receivers, transmitters or transceivers that are part of the mobile device.
Generally, transmission and reception capabilities of an antenna scale with antenna size. However, the size of conventional mobile devices, particularly that of handheld mobile devices, restricts antenna size and placement. For example, not only can the small form factor of handheld mobile devices restrict the physical size of the antenna, but interference between the antenna and other mobile device components can influence antenna design as well. Some mobile devices have antennas that are extendable or that protrude from the mobile device housing in an attempt to improve antenna performance, but these features may not be desirable as some consumers prefer aesthetically pleasing mobile devices having clean lines and a sleek look.
Some conventional mobile devices utilize antennas included in an attached accessory device to improve signal reception. For example, some conventional mobile media players use the wires extending from the mobile device to earbuds of a connected headphone set as an antenna source. However, the headphone adapter or jack of a mobile device can be arranged along the same edge of the mobile device as a dock connector. Thus, when such a mobile device is connected to a dock, the device cannot take advantage of a headphone antenna. Even if a headphone adapter is arranged on the mobile device such that a headphone can be connected to the mobile device when the mobile device is connected to a dock, a headphone set may not be readily available.
Accordingly, it is desirable to provide mobile device accessory devices that can provide an antenna for use by an attached mobile device. It is further desirable to provide mobile devices that can detect, select and use antennas supported by mobile phone accessories.